bleeding brakes
Re: bleeding brakes
It was my understanding that within the piston itself there is a small spring and this small spring works with the pin like rod that it fits onto when the piston is the bore. My front caliper spring has a break in it and I am told that is why I can't get it to release all the way. Its not grabbing but maintaining enough pressure so that the free wheel spin is not like its opposite wheel. As a remedy I honed the bore a touch thinking maybe the new bore tolerances were too tight to the new seals. No luck...same result. Please correct me if I'm off....
Cory
Cory
Re: bleeding brakes
John: Check the small hole behind the MC o-ring which open to the reservior. That was what caused my SWB to hold pressure. The o-ring had swollen and the piston was not able to clear the orifice. We took a .020" cut off the piston. Probably not the best procedure, but it worked. Bob
-
- Posts: 1908
- Joined: Wed Sep 04, 2002 12:13 am
- Location: San Francisco Area
Re: bleeding brakes
Thanks Bob and Kerry for the explanation. I fixed the problem. The replacement front seal I had bought for the EQ valve was a little thinner than the original, so I had cut out a filler from rubber material to take up the slack. Apparently that was interfering with the operation of the EQ valve. I removed the extra piece.
The issue now is that there is some slight drag on all four wheels, not enough to keep the car from rolling, but enough to take effort to turn the splined hub with your wrist. The wheel cylinders are all lined with stainless sleeves and every other part in the system is either new or refurbished. The system is bled and the pedal is incredibly firm. From the explanation Kerry gave on the method of wheel cylinder retraction, I can see why the pistons may not retract all the way the way the drum brake shoes retract with the spring assist. So, maybe things will loosen up with use.
Thank you all for your advice.
john
The issue now is that there is some slight drag on all four wheels, not enough to keep the car from rolling, but enough to take effort to turn the splined hub with your wrist. The wheel cylinders are all lined with stainless sleeves and every other part in the system is either new or refurbished. The system is bled and the pedal is incredibly firm. From the explanation Kerry gave on the method of wheel cylinder retraction, I can see why the pistons may not retract all the way the way the drum brake shoes retract with the spring assist. So, maybe things will loosen up with use.
Thank you all for your advice.
john
PF Coupe
Re: bleeding brakes
I have always been taught that the little retractor pins and springs are the mechanism which causes the pads to retract when the pressure is released. The other mechanism is the slight runout of the rotor moving the pistons back into the caliper cylinders.
-
- Posts: 1908
- Joined: Wed Sep 04, 2002 12:13 am
- Location: San Francisco Area
Re: bleeding brakes
John: I found this online. Maybe it will do the trick. http://mgaguru.com/mgtech/twincam/tc207.htm
-
- Posts: 1908
- Joined: Wed Sep 04, 2002 12:13 am
- Location: San Francisco Area
Re: bleeding brakes
Bob, thanks for posting this, it saved my life. The last sentence of the second paragraph turned on the bulb in my head and I spotted my problem right away. Damned amateurs!
john
john
PF Coupe
Re: bleeding brakes
Can someone please advise me of the purpose of the small hole (Which I cannot find) in the booster cylinder. The only purpose I can think of would to allow air to bleed out, but that should be accomplished by the clearance between the rod on the end of the piston and the casting. Bob A
-
- Posts: 1908
- Joined: Wed Sep 04, 2002 12:13 am
- Location: San Francisco Area
Re: bleeding brakes
Can not been overseen John with good eyes ,but its maybe only 10 mu.
Its located under the bracket from the chassis ,see my earlier post here.
ciao
C.
Its located under the bracket from the chassis ,see my earlier post here.
ciao
C.
- Attachments
-
- IMG_3910.jpg (90.55 KiB) Viewed 11833 times
-
- IMG_3911.jpg (93.14 KiB) Viewed 11833 times
-
- IMG_3912.jpg (113.27 KiB) Viewed 11833 times
-
- Posts: 1908
- Joined: Wed Sep 04, 2002 12:13 am
- Location: San Francisco Area
Re: bleeding brakes
Thanks Cornelis. Is the one in your picture the longer type that goes on the earlier cars?
john
john
PF Coupe
-
- Posts: 1908
- Joined: Wed Sep 04, 2002 12:13 am
- Location: San Francisco Area
Re: bleeding brakes
Cornelis, I see that this is the cast iron type that goes on the earlier cars, like my PF coupe. The later cars have smaller cylinder made of cast aluminum.
john
john
PF Coupe
Re: bleeding brakes
My question was "What is the purpose of the small hole"? It must have something to do with air pressure, but since the shaft at the end of the cylinder is not really air tight, I wonder that the hole is for. I have found that usually there are not machining features put in parts without there being a reason. Bob A